Norovirus outbreak closes oyster farms off Denman Island, Deep Bay

Two shellfish farms off mid-Vancouver Island have been closed following an outbreak of norovirus associated with the consumption of raw B.C. oysters. — File photo

The BC Centre for Disease Control (BCCDC) has linked an outbreak of norovirus associated with raw B.C. oysters, and two area oyster farms implicated in the outbreak have been closed, the Provincial Health Services Authority announced Monday, April 9.

The BCCDC is warning raw shellfish consumers to take steps to protect their health following an increase in cases of norovirus associated with consumption of raw B.C. oysters. Since early March 2018, approximately 40 cases of acute gastrointestinal illness have been reported to public health authorities in B.C.

Two oyster farms implicated in the outbreak have been closed by federal authorities.

Fisheries and Oceans Canada posted a sanitary emergency closure notice March 23 for oysters at a farm off the west coast of Denman Island. Another emergency sanitary closure was posted for oysters in a portion of Deep Bay on April 5. In both cases, the prohibition will be in effect “until further notice” and “until further information can be obtained and assessed.”

All of the ill people reported consuming raw B.C. oysters. Laboratory testing has confirmed the presence of norovirus in some of the cases and it is suspected in the others. The investigation is ongoing.

In order to kill norovirus and other pathogens, the BCCDC recommends consumers cook oysters thoroughly, to an internal temperature of 90˚C (degrees Celsius) for 90 seconds. Consumption of raw oysters is not encouraged.

In late 2016 and early 2017, 347 norovirus outbreak cases associated with raw or undercooked B.C. oysters were reported in B.C., Alberta and Ontario. The outbreak was declared over in April, 2017. Learn more in the BCCDC’s Annual Summary of Reportable Diseases, under Norovirus.

While the precise sources of contamination have not been identified, human sewage in the marine environment is currently believed to be the most plausible cause of shellfish contamination.

Anyone becoming ill with diarrhea and vomiting after eating shellfish should call BC HealthLink at 811. If symptoms are severe or persist, they should see their physician.

Oyster-related illness can be reported to your local health authority for investigation and follow-up.

For most people, norovirus is a self-limiting illness and people will recover on their own with proper hydration and rest. On rare occasions, dehydration may be severe and require medical attention.